Mercury relay



1955 1. L. MITCHELL MERCURY RELAY Filed Oct. 51, 1961 INVENTOR IEVING- L. MrrcHEu.

ATTORNEYS 3,166,654 Patented J an. 1 9, 1965 United StatesPatent Ofiice 3,166,654 MERCURY RELAY Irving L. Mitchell, Rockville Centre, N.Y., assignor to Ebert Electronics Corporation, Queens Village, N.Y., a corporation of New York Filed Oct. 31, 1961, Ser. No. 149,012 4 Claims. (Cl. 200-412) This invention relates to mercury relays of the displacer type wherein a pool of mercury is displaced in order to provide contact between spaced electrodes, and more particularly to a mercury relay of the displacer type wherein the conducting path between the spaced electrodes is either normally open or normally closed depending upon the arrangement of standard parts.

Inthe design of mercury relays it is desirable to produce relays having different operating characteristics without the necessity of requiring different operative parts or parts of different sizes depending upon the particular use. The advantage of using standard parts is obvious in that manufacturing and replacement costs are reduced, without any loss of utility to the consumer.

It is also a diificulty in the design of mercury relays in general and including those of normally open or normally closed type to provide a relay wherein the operating characteristics thereof remain constant over a long period of time of heavy use. A contributing factor to a change in the operating characteristics of a mercury relay is due to the friction between the moving parts thereof causing wear. Another difiiculty leading to inconsistent operation arises in relays where the container is of paramagnetic material causing the setting up of eddy currents which have an electromagnetic and thermal effect on the moving elements. In conventional mercury relays of the mercury displacer type it has been necessary to provide cumbersome insulation for the armature in the container. By providing a container of material having the properties of being an insulator, and of also being unaffected by electromagnetic fields, such cumbersome insulation is eliminated. Insulation has also been required in previous relays between the armature element and the electrodes because the armature is usually of a material having electrically conducting properties. Such insulation adds to the already cumbersome insulation in the relays of the previous types, thereby causing a great amount of additional weight to the armature, said weight being added to the amount which must be actuated for movement by the electromagnetic energizing coils.

These and other disadvantages are overcome by the present invention in which there is provided a container of material having insulating and diamagnetic properties, said material also, having the property of being self-lubrieating. In thecontainer is a pool of mercury displaceable by a normally buoyant armature element which is in sliding frictional engagement with the inside walls ofthe container through the medium of self-lubricating studs, said studs preferably also being of the same type of material as is the container. The armature element is in the form of a tube on the inside of which is a tubular liner having insulating properties suitably bonded thereto. The liner element is preferably of a ceramic type material having the properties of being an insulator, diamagnetic, andchemically inert. In order to provide a mercury relay which is normally closed, a compression spring is mounted at the upper end of the container, and exerts a downward force against the armature element which normally seeks a higher position in the container due to its normal buoyancy in the pool of'mercury therein. Two spaced electrodes are located in the container, one of the spaced electrodes being surrounded by a cup made of material having insulating properties. The container is surrounded by an electromagnetic energizing coil at an appropriate location. When the electromagnetic coil is energized, due to the electromagnetic field and the tendency of the buoyant armature to rise in the mercury, the armature element is moved upwardly in the container against the bias of the compression spring, thereby dropping the level of the pool of mercury below that of the electrode having the surrounding insulating cup, thus breaking the electrically conducting path between the two spaced electrodes. Upon de-energization of the coil, the compression spring forces the armature element downwardly in the container thus raising the level of mercury above that of the two spaced electrodes in the bottom of the container, thereby re-establishing electrical contact therebetween.

In order to provide a normally open relay, according to the invention the compression spirng is located in the bottom of the container and exerts a force against the armature element in a manner to bias the armature element against a tendency to sink to its normal position of buoyancy in the pool of mercury, in which position the level of a pool of mercury is just below that of the cup of the insulated electrode. When the electromagnetic energizing coil is energized, the armature is pulled down against the bias of the compression spring thereby displacing the pool of mercury so that its top level thereof exceeds the level of the insulated cup of one of the spaced electrodes. Mercury enters the cup and establishes a path of electrical conduction between the two spaced electrodes and the container. When the coils are de-energized, the compression spring causes the armature element to move upwardly in the container to drop the level of mercury below that of the insulated cup, thereby breaking the electrical conducting path between the two spaced electrodes. Due to the self-lubricating properties of the container and of the studs mounted on the armature which are in sliding frictional engagement with the container, a minimum of wear is realized in the relay according to the invention. Thus the mercury relay of the invention is capable to being operated over a long period of time with a minimum change of operating characteristics thereof. Moreover, due to the light weight of the armature element, energizing coils requiring low current may be utilized, thereby reducing the effects of eddy currents and temperature changes on the mercury relay.

Accordingly, it is an object of this invention to provide a mercury relay of the displacer type in which the arrangement of the parts may be varied to provide either a normally closed or normally open operating characteristic.

It is another object of this invention to provide a normally open or normally closed mercury relay of the displacer type which is of simple construction, rugged, reliable, and in which there is a minimum change of op erating characteristics over a long period of use.

It is another object of this invention to provide a mercury relay of the normally closed type or of the normally opened type wherein there is provideda mercury pool container of diamagnetic, insulating material and mercury displacing element insulated from spaced electrodes therein and sliding in a self-lubricative in the container, the deleterious effects of temperature changes, eddy currents, and wear caused by friction are thereby being eliminated or reduced to a minimum therein.

It is yet another object of this invention-to provide in a mercury relay of the mercury displacing typein which a mercury displacing element requires only a minimum of insulation.

These and other objects and features of the invention willfbe better understood by referring to the drawings in which:

' FIGURE 1 is a longitudinal cross-sectional view of a i normally closed relay according to the invention;

FIGURE 2 is a longitudinal cross-sectional view of a normally open relay according to the invention, and

FIGURE 3 is a longitudinal cross-sectional view of an illustrative embodiment of a mercury relay according to the invention in which the electrodes are provided at opposite ends of a container.

Referring to FIGURE 1, a normally closed relay according to the invention is shown generally at having a container 12 which may be of glass, metal, plastic, but which is preferably of nylon or nylon filled with fiberglass. At the lower end of the container 12 and suitably sealed thereinto in a well known manner by epoxy resin is an insulated electrode 14 and a bare electrode 16 immersed in the mercury for continuous contact therewith. At the upper end of insulated electrode 14 is a cup made of suitable insulating material surrounding the bare end of the electrode. cury 18, a variable level of which is shown at 211. A mercury displacing element indicated at 22 is buoyant therein, and includes an armature portion 24 and a liner portion 26 which is made of'a chemically inert material having insulating and diamagnetic properties. Liner portion 26 is suitably fastened or bonded to the armature portion 24 in a suitable manner.

The tubular mercury displacing element 22 is provided with studs 28 made of a self-lubricating material such as nylon, or delrin, and are mounted on the armature portion of the mercury displacing element. Studs In the container is a pool of mer- V self-lubricating properties.

I between the bottom thereof and the lower end of the mercury displacing element 22 may be provided to protect the relay against shock.

A normally open relay according to the invention is shown in FIGURE 2- at 36 having a container 12 which is exactly similar to that shown in FIGURE 1. Those elements of FIGURE 2 which are exactly similar to those of FIGURE 1 will be accorded to the same reference numerals for purposes of convenience. Container 12 may be of the same material as discussed in conjunction with FIGURE 1 and is preferably, therefore, of nylon filled with fiberglass to obtain diamagnetic, insulating and Suitably sealed into the bottom of container 12 are electrodes 14- and 16, electrode 14 being an insulated electrode with a cup 15 at the top thereof surrounding the bare electrode portion and 16 being a bare electrode. Mounted in the inside of the container 12 at the bottom thereof is a compression spring ment described in conjunction with FIGURE 1, and in- 28 are 'in frictional engagement with the inside walls of container 12 so that armature element 22 slides up and down therein. Since the material of the container 12 and the studs 28 are preferably of the same self-lubricating characteristics, there is very little frictional resistance to the movement of the mercury displacing member 22 by the container 12.

A compression spring 30 is located in the top of the container 12 and presses against the mercury displacing element 22, thereby biasing element 22 downwardly against its buoyant tendencies in the mercury pool 18. When spring 30 and element 22 are in equilibrium, level 29 is normally above the level of cup 16. An energizing electromagnetic coil 32 is suitably mounted to surround a portion of the container 12 so that upon energization the mercury displacing element 22 due to its armature portion 24 thereon is attracted upwardly by the electromagnetic field in the container 12. The electromagnetic energizing coil 32 may be energized by a suitable source of alternating or direct current (not'shown).

In operation of the normally closed relay of FIGURE 1, when the energizing coil 32 is not energized, the mercury 18 supplies a conducting path between the electrodes 14 and 16. This is due to the fact that compression spring 30 pressing down on the mercury displacing element 22 prevents said element 22 from rising in the pool of mercury 18 due to its natural buoyancy therein.

However, upon energization of coil 32, the mercury dis placing element 22 is pulled upwardly against the bias of the spring 30 by the electromagnetic field produced by the coil 32, thereby causing the level 20 of the mercury pool to drop below the top of the cup 16 of the insulated electrode 14. When the level 20 is below the level of thetop of insulated cup 16, then an electricalconducting path between electrodes 14 and 16 is interrupted, thereby breaking the contact therebetween. Any residual mercury in the cup 16 has no effect on the electrical conductive path since the electrode 14 is completely insulated within the cup 16.

Upon de-energization of the coil 32, the force of the spring 30 pushes the mercury displacing element 22 against its buoyant tendencies into the pool of mercury 18, thereby causing the level 20 of the mercury 18 to rise in the container 12. When the level 20 of the mercury rises abovethe top of the cup 16, contact is once again established between the electrodes 14 and 16. A cushion- =ing spring shown at 34 in the bottom of the container eludes an armature portion 24, a ceramic liner portion 26, and studs 28 which are preferably of a self-lubricating material to insure minimum sliding friction with the inside walls of container 12 as armature element is moved up and down therein.

An electromagnetic energizing coil indicated at 32 surrounds a portion of container 12. A pool of mercury 40 is contained by the container 12 to such a level indicated at 42, that when coil 32 is de-energized, the level 42 of the mercury pool 40 is below the level of the top of the cup 15. The distance of the level 42 below the top of cup 15 is such that the displacement thereof by mercury displacing element 22 will cause the level 42 to exceed the top of the cup 15 when actuated by energizing coil 32; Acushioning spring indicated at 44 may be provided to protect the relay from shock.

In the operation of the normally open relay shown in FIGURE 2, when electromagnetic coil 32 is energized, mercury displacing element 22 due to the field etfect on its armature portion 24 is attracted downwardly in the container, thereby displacing mercury upwardly in the 7 v the mercury to drop in the container. When the level 58 of the mercury drops sufliciently due to the upward motion of the mercury displacing member 46, contact between electrodes 38 and 40 is broken. Due tothe action of compression spring 44, mercury displacing element 46 is lifted to a position above its position of natural buoyancy in the pool of mercury 56.

Another embodiment of the invention is shown in FIG- URE 3 wherein the spaced electrodes are sealably mounted in opposite ends of a container. In FIGURE 3 a normally closed relay is shown, it being understood that a normally open relay having electrodes at each end of the container may be provided according to the invention.

In FIGURE 3, a container 46, which may comprise the same material as those of FIGURES 1 and 2, is provided with an insulated electrode 48 atthe upper end and a bareelectrode 50 at the other end sealablymounted therein. Insulated electrode 48 has a bare end suitably cury displacing element 56 is separated from the inside surface of container as by self-lubricating studs 62 for sliding engagement therewith. A compression spring 63 positioned in the top of container 46 biases the mercury displacing element 56 below its normal position of buoyancy in mercury pool 54. An energizing coil 64 surrounds a portion of container 46 to actuate displacement of the mercury displacing element 56.

As shown in FEGURE 3, the level of mercury pool 54 is shown above the level of cup 52 so that the relay is normally closed. In operation, upon energization of coil 64 from a suitable AC. or DC. source, the mercury displacing element 56 is moved upward in the container due to the flux of the coil 64 coacting with the armature portion 58 thereof, thereby displacing mercury pool 54 downward in the container 46. The downward displacement of the mercury pool 54 as element 56 moves upwardly to a position of equilibrium with the flux of coil 64 and spring 63 causes the level of mercury to drop below cup 52, thereby breaking contact between the electrodes 4S and 50. De-energization of coil 64 permits Spring 63 to force element 56 downwardly, the mercury then being displaced upwardly to exceed the level of cup 52 so that contact is re-established between electrodes 48 and 5t). 7

It is understood that a normally open relay may be provided for a container having electrodes at opposite ends by placing a compression spring beneath element 56, by adjusting the level of mercury to normally be beneath the level of cup 52, and by positioning the coil 64 so that upon energization thereof, the element 56 is pulled downward to cause the upwardly displaced mercury to exceed the level of cup 52, thereby establishing contact between the spaced electrodes 48 and 50. This arrangement would be similar to that shown in FIG- URE 2 except that the insulated electrode 14 would be mounted at the opposite end of the container in the manner shown in FIGURE 3.

It is also understood that other resilient means may be used instead of a compression spring to bias the armature, such as tension springs mounted in a manner opposite to the compression spring, or resilient material such as rubber or having the same properties as rubber.

It is appreciated that in accordance with the invention the only difference between the normally closed and normally open relays are the mercury level, the positions and size or'strength of the compression spring and the location of the energizing coil. Thus the invention affords the mercury relays of the mercury displacing type a minimum of change necessary in the manufacture thereof of basic elements to produce either normally closed or normally open mercury relays.

It is understood thatthe forms of my invention as embodied in the above exemplary illustrations as herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of the parts may be resorted to without departing from the spirit of my invention, which is limited only by the following claims.

What is claimed is: v

l. A. mercury relay of the displacer type comprising a pool of mercury, a container for said pool of mercury, energizing coils surrounding a portion of said container to produce, when energized, an electromagnetic field therein, a pair of spaced electrodes mounted therein at least one of which is always immersed in said pool of mercury, insulating means surrounding the other of said pair of electrodes including a cup portion spaced from the bare end thereof, a mercury displacing element normally buoyant in said mercury pool and movable toward the central plane of said coil in response to the energization mercury displacing element against the direction of movemerit thereof responsive to the energization of said coil, the position of said resilient means being selectively either above or below said mercury displacing element in said container, whereby when the level of said mercury pool is normally above said cup and the resilient means is positioned above said mercury displacing element, the movement of said displacing element responsive to the energization of said coils causes the mercury pool to be displaced, and the electrical contact between said electrodes to be broken, and when the level of said mercury pool is normally below said cup and said resilient means is positioned below said mercury displacing element in said container the movement of said displacing element due to the energization of said coil causes the mercury pool to be displaced thereby establishing electrical contact between said electrodes.

2. Apparatus according to claim 1 wherein the container is comprised of insulating material having the property of self-lubrication, and a plurality of studs mounted on said mercury displacing element, said studs eing in sliding engagement with the inside surface of said container.

3 Apparatus according to claim 1 wherein said resilient means is a compression spring and said mercury displac ing element includes an armature portion tubular in form and having an insulating liner on the inside portion thereof, and a plurality of studs mounted on said armature portion for sliding engagement with the inside surface of said container.

4. A mercury switch of the displacer type for selective adaption to either normally open or normally closed operation, said switch comprising a container, a pool of mercury disposed within said container, a pair of spaced electrodes projecting into said container, one of said electrodes being always immersed in said mercury pool, mercury displacing means having a normal buoyant position in said mercury pool, means for actuably moving said displacing means to vary the depth of partial submergence thereof in said pool and thereby to vary the level of said pool within said container, means resiliently biasing said displacing means against said actutable movement, said biasing means being selectively positionable within said container to bias said displacing means to a predetermined position of either greater or less partial submergence than that of said normal buoyant position thereof, the other of said electrodes being in electrically conductive contact with said mercury pool for said normally closed switch operation and being insulated from said pool for said normally open switch operation when said displacing means is biased respectively to said predetermined position of said greater partial submergence and to said predetermined position of less partial submergence, said actuable movement of said displacing means to vary the level of said pool being suiiicient to break and make electrical contact between said pair of electrodes through said pool in said normally closed and normally open switch operation, respectively.

References Cited by the Examiner UNITED STATES PATENTS 1,971,934 8/34 Hatay 200-112 2,113,595 4/38 Larson et a1 200l12 2,658,124 11/53 Weimer 200- -112 X BERNARD A. GILHEANY, Primary Examiner.

ROBERT SCHAEFER, Examiner. 

1. A MERCURY RELAY OF THE DISPLACER TYPE COMPRISING A POOL OF MERCURY, A CONTAINER FOR SAID POOL OF MERCURY, ENERGIZING COILS SURROUNDING A PORTION OF SAID CONTAINER TO PRODUCE, WHEN ENERGIZED, AN ELECTROMAGNETIC FIELD THEREIN, A PAIR OF SPACED ELECTRODES MOUNTED THEREIN AT LEAST ONE OF WHICH IS ALWAYS IMMERSED IN SAID POOL OF MERCURY, INSULATING MEANS SURROUNDING THE OTHER OF SAID PAIR OF ELECTRODES INCLUDING A CUP PORTION SPACED FROM THE BARE END THEREOF, A MERCURY DISPLACING ELEMENT NORMALLY BUOYANT IN SAID MERCURY POOL AND MOVABLE TOWARD THE CENTRAL PLANE OF SAID COIL IN RESPONSE TO THE ENERGIZATION OF SAID COILS TO DISPLACE AN AMOUNT OF MERCURY IN SAID POOL, SAID ELEMENT BEING SUBSTANTIALLY SYMMETRIC AS SEEN FROM ABOVE AND BELOW, RESILIENT MEANS BIASING SAID MERCURY DISPLACING ELEMENT AGAINST THE DIRECTION OF MOVEMENT THEREOF RESPONSIVE TO THE ENERGIZATION OF SAID COIL, THE POSITION OF SAID RESILIENT MEANS BEING SELECTIVELY EITHER ABOVE OR BELOW SAID MERCURY DISPLACING ELEMENT IN SAID CONTAINER, WHEREBY WHEN THE LEVEL OF SAID MERCURY POOL IS NORMALLY ABOVE SAID CUP AND THE RESILIENT MEANS IS POSITIONED ABOVE SAID MERCURY DISPLACING ELEMENT, THE MOVEMENT OF SAID DISPLACING ELEMENT RESPONSIVE TO THE ENERGIZATION OF SAID COILS CAUSES THE MERCURY POOL TO BE DISPLACED, AND THE ELECTRICAL CONTACT BETWEEN SAID ELECTRODES TO BE BROKEN, AND WHEN THE LEVEL OF SAID MERCURY POOL IS NORMALLY BELOW SAID CUP AND SAID RESILIENT MEANS IS POSITIONED BELOW SAID MERCURY DISPLACING ELEMENT IN SAID CONTAINER THE MOVEMENT OF SAID DISPLACING ELEMENT DUE TO THE ENERGIZATION OF SAID COIL CAUSES THE MERCURY POOL TO BE DISPLACED THEREBY ESTABLISHING ELECTRICAL CONTACT BETWEEN SAID ELECTRODES. 